Content-Aware Caching and Proxy operations by a transit network device, when placed in Radio Access Networks (RAN) in UMTS and LTE networks, are described in copending U.S. Patent Publication No. 2010-0034089, the disclosure of which is incorporated by reference.
3GPP Release 10 Specifications define the Selective IP Traffic Offload (SIPTO) function in a transit network device (Traffic Offload Device) that intercepts the IuPS interface in the UMTS network. It offloads portions of SGSN/GGSN (Serving GPRS Support Node/Gateway GPRS Support Node) or SGW/PGW (Serving Gateway/PDN Gateway) traffic to an offload interface attached to the Internet or to the operator's data network. These specifications also define alternative solutions for Traffic Offload in the UMTS and LTE networks. The offload policies in these specifications use Access Point Name (APN) information or implement offload control specified by the SGSN/MME in the control plane.
It should be noted that the TOF (Traffic Offload Function) device defined in the 3GPP specification is a gateway device which forwards packets from one interface to either the offload interface or to the default SGSN/GGSN or SGW/PGW. However, it is not a content caching and content aware proxy device.
The SIPTO feature in these specifications does not specify caching content nor do these specifications define SIPTO devices capable of originating traffic. For example, these specifications do not define terminating a TCP session and delivering stored content from cache. Delivering content from cache, for example responding to a http request from Radio Network Controller (RNC) or eNodeB, requires establishing an association between two unidirectional GTP-U tunnels and mapping their bearer-plane User Equipment (UE) IP address. The caching device needs to encapsulate http responses for locally cached objects with the GTP-U tunnel ID of the RNC or eNodeB for the corresponding UE from these learned associations. Similarly, while performing Selective IP Traffic Offload function, the transit network device terminates the per UE GTP-U tunnel of traffic received from E-NodeB/RNC and forwards traffic based on bearer plane IP addresses, and encapsulates the traffic received from the offload interface with the GTP-U tunnel corresponding to the specific UE and bearer IP address while forwarding to the eNodeB/RNC.
The 3GPP specifications define learning the GTP-U tunnel and Bearer IP Addresses from the S11 interface in the LTE architecture. Also the S1-AP specification contains protocol elements that contain bearer IP addresses and the user plane GTP-Tunnel-IDs; however bearer IP addresses are contained within the NAS portion of the PDUs which may be encrypted and/or in certain deployments the logical S1AP may not available at specific deployment locations.
However, these specifications do not provide guidance regarding associating tunnels when the TOF or SIPTO device acts as a transparent proxy device. Thus, to properly implant local content caching, a method is needed to identify and associate pairs of GTP-U tunnels for each UE. Thus the current invention identifies methods of establishing association between the two unidirectional flows and the corresponding bearer IP addresses.